How to change the location of an addon in the UI
It's not a good idea to do that, but here is how anyway. Be aware that this may break add-ons.
What you need to be looking for is were the panels because they determine were UI elements are placed. The panel classes can be identified by their inheritance from bpy.types.Panel, although depending on how modules are imported it might just say Panel. Starting from Blender 2.8 there is a mandatory naming convention by which the class name of the panel should also contain _PT_.  Take as an example the following excerpt that defines a panel:
class SOME_COOL_ADDON_PT_settings(bpy.types.Panel):
    bl_idname = &quot;SOME_COOL_ADDON_PT_settings&quot;
    bl_label = &quot;Setting for cool addon&quot;
    bl_space_type = &quot;VIEW_3D&quot;
    bl_region_type = &quot;UI&quot;
    bl_category = &quot;View&quot; 

    ...

The placement in the UI is determined by bl_space_type, bl_region_type and bl_category. This means the panel is created in the 3D View in the right hand panel (which can open/close by pressing N) in the View tab. You could change the tab to Tool by changing the bl_category = &quot;Tool&quot;.